Bismuth sesquioxide ($$\hbox {Bi}_2\hbox {O}_3$$ Bi 2 O 3 ) draws much attention due to wide variety of phases in which it exists depending on the temperature. Among them, $$\delta$$ δ phase is specially interesting because of its high oxide ion conductivity and prospects of applications as an electrolyte in fuel cells. Unfortunately, it is stable only in a narrow temperature range ca. 730–830 $$^{\circ }$$ ∘ C. Our group has developed a facile and reproducible two-stage method of stabilizing $$\hbox {Bi}_2\hbox {O}_3$$ Bi 2 O 3 crystalline phases confined in nanocrystallites embedded in amorphous matrix. In the first stage, glassy materials were obtained by a routine melt-quenching method: pure $$\hbox {Bi}_2\hbox {O}_3$$ Bi 2 O 3 powders were melted in porcelain crucibles and fast-cooled down to room temperature. In the second step, the materials were appropriately heat-treated to induce formation of crystallites of $$\beta$$ β , $$\delta$$ δ or $$\gamma$$ γ $$\hbox {Bi}_2\hbox {O}_3$$ Bi 2 O 3 phases confined in a glassy matrix, depending on the process conditions. It was found out that the vitrification of the initial $$\hbox {Bi}_2\hbox {O}_3$$ Bi 2 O 3 and the subsequent nanocrystallization were unexpectedly possible due to the presence of some Al, and Si impurities from the crucibles. Systematic DTA, XRD, optical, Raman and SEM/EDS studies were carried out to investigate the influence of the syntheses processes and allowed us to determine conditions under which the particular phases appear and remain stable down to room temperature.

A glassy sample with a nominal formula LiMn 1−3x/2 V x BO 3 (where x = 0.05) was synthesised using the melt-quenching method. Material was characterised by differential thermal analysis (DTA), X-ray diffactometry (XRD) at room temperature and as a function of temperature (HT-XRD), X-ray photoelectron spectroscopy (XPS), impedance spectroscopy (IS) and scanning electron microscopy (SEM). Dependences of glass transition and crystallisation temperatures on the heating rate in DTA experiments were determined. The initial value of electrical conductivity of the glass was 1.4 × 10 −15 Scm −1. It was significantly increased by a proper thermal nanocrystallisation. The maximum value was higher by 6 orders of magnitude and reached 2.6 × 10 −9 Scm −1 at room temperature. Expected crystalline phases (i.e. monoclinic and hexagonal LiMnBO 3) upon heating were identified and assigned to thermal events observed with DTA. Microstructure of nanocrystalline samples observed by SEM revealed nanocrystalline grains noticeably smaller than 100 nm. Results explaining nanocrystallisation process are coherent.

Inorganic fluorophosphate glasses doped with Eu$$^{2+}$$ 2 + /Eu$$^{3+}$$ 3 + are potential candidates for phosphors for commercial white LEDs. This report presents a fast, inexpensive and effective method of controlling the relative concentrations of Eu$$^{2+}$$ 2 + /Eu$$^{3+}$$ 3 + photoluminescent centers in these glasses. The technique consists of a fast quenching of the melt of initial reagents under appropriate conditions. Eu$$^{2+}$$ 2 + /Eu$$^{3+}$$ 3 + ratio was controlled by carrying out the melting under a reducing atmosphere at a temperature between 1000 and 1200 $$^\circ$$ ∘ C for periods of 5 to 15 minutes. The reducing atmosphere was provided by a ’double crucible’ technique and did not require special gas lines during the synthesis. The samples were studied by several complementary experimental methods (X-ray diffractometry—XRD, X-ray photoelectron spectroscopy—XPS, photoluminescence—PL—and photoluminescence excitation—PLE—spectroscopies as well as optical transmission spectroscopy). It was shown that the syntheses resulted in amorphous materials with different relative Eu$$^{2+}$$ 2 + /Eu$$^{3+}$$ 3 + concentration ratios, strongly dependent on the preparation conditions: the temperature and the time of melting in a reducing atmosphere. Moreover, changes in these ratios strongly affected the materials’ PL and PLE spectra. Demonstration of reproducible smooth transition from amaranth to blue luminescence color, with white in between, was the most spectacular result of this work.